Alloy



A191111, 1941. E FET; 236,899

' I ALLOY y Filed Feb. 17, 1939 l Gram, Calcium Sil'mon.,

Patented Apr. 1, i941 ALLOY Erich Fetz, Newark, N.

Driver Co., Jersey li., Newark, N. i., acorporation of New assigner to Wilbur lB.

Application February 17, 1939, Serial No. 256,966 4 Claims. (Cl. i5-171) The invention relates to alloys and more particularly to improvements in the life characteristics of alloys adapted for electrical resistance uses.

In my co-pending lapplication, Serial No. 231,597, entitled Alloy, I have disclosed a product consisting essentially of nickel and chromium, or,` nickel, chromium and iron, with either of which basic alloys boron is compounded for the purpose of improving the hot workability of the resultant metal.

This invention has for its principal object the improvement of the life characteristics of valloys of the type disclosed in my beforementioned a-pplication,

It is yet another object of the invention to attain desirable life characteristics in alloys of the beforementioned cl-ass Without an attendant decrease in the Workability or forgeability of the resultant product.

A more specific object of the invention resides in the provision of an alloy of relatively longer life characteristic than has heretofore been attainable Without detracting from lthe commercial utility of the product.

It is a Well established hypothesis in the art that the life of resistance alloys such, for example, as nickel-chromium, and nickel-chromiumiron, when submitted to high temperatures, is a function to a large ex-tent of the crystalline structure of the product. This physical characteristic of the alloy is greatly influenced by the high afnity of chromium for oxygen, nitrogen and cary bon at the high melting temperatures employed in the manufacturing operation. The molten metal is contaminated by the formation of oxides, nitrides, carbides, etc., which accumulate at the crystal boundaries upon solidication. When thealloy is subsequently raised to the operating temperatures common to resistance wire applications, these non-metallic accumulations at the crystal, or grain boundaries, are presumed to react diierently from the pure metaldue to their different co-eicients 'of expansion, with the resultI that further oxidation occurs between the bodies of thel crystals themselves until the Wire, or such other form as the resistance element may take, fails physically. i

It has accordingly been the practice to add such substances as silicon, aluminum, calcium, magnesium, beryllium, zirconium, -ceriurn, etc., to the basic alloy with a. view to removing the non-mef tallic impurities introduced duringthe melting process, as Well as to increase the oxidation re- Standards, 1936, page 734.y

sistance of the finished product at service tem'- peratures.

In the United States Pa-tent to Hunter No. 2,005,423, for example, i-t was proposed that calcium be added to a basic nickel-chromium alloy in quantities ranging from 0.03 to 0.2% to improve the life characteristics of the finished product. Similarly, in the patents to Lohr, Nos. 2,005,430, 2,005,431, 2,005,433, and 2,047,916, the benecial effects of additions of such elements as molybdenum, zirconium and calcium to basic nickel :and chromium, or, nickel-chromium-iron alloys is clearly pointed out.

I have found, however, that the presence of any one or more of these oxidation resisting diluents impairs the hot Workability of the product and that any effort to attain ideal life characteristics by increasing the percentage of diluent employed renders the product altogether unforgeable and, thus, commercially useless.

For example, a series of melts were made in which 150, 160175, 190 and iinally 250 grams of calcium silicon were added to the basic lalloy of nickel and chromium. 'Ihe alloys containing 150 and 160 grams respectively of calcium silicon showed poor results in forging tests, While those alloys containing the relatively higher percentages of calcium silicon were altogether unforgeable. Thus, it will be apparent that the percentage of the life imparting diluents which may lbe employed in any given alloy is a function of, and limited by, the ability to work the nished product.' l

I have found .that the addition of boron to the basic alloy permits of the use of greater per-` centages of the life imparting diluents without adversely aifecting the forgea-bility of the finished alloy.

To illustrate the effect of the presence of boron upon the total percentage of a life imparting diluent Which may be added to the basic alloy without destroying its forgeability characteristics, I have prepared nickel-chromium alloys Vcontaining the identical quantities of .calcium silicon set forth in the above enumeratedtests with the addition in each instance of 50 grams of manganese boron. Y

For .the purpose of determining the life of these 'alloys at high temperatures, I have tested that series which contained boron -by the method of test youtlined in American Society for Testing Materials, Designation 1376-36, Book of A. S. T. M.

diluents l "silicon because wouiaentaiireiativeiy A obtainable commerciallyjur -jionn vof corn- Test specimen 4. (a) The test specimen shall not be larger than No. A. W. G. nor smaller than No. 22 A.VW. G. The length of Wire selected for tests shall be such as to permit the use of a 12" test length between the two terminals.

Mounting of specimens 5. (a) The test specimen shallbe mounted on lthe test board in a vertical position and shall be spaced as follows:

nches n Distance' between test boardand specimens-.. 2 Distance between specimens Distancevbetween specimen and shield 2 Distance between upper bus bar and mercury v cup Temperature of te'st '7. The temperature of test shall be specie and shall .be chosen so as to give a test life of approximately 100 hrs.

Procedure 8. The procedure shall be carried out a's described in paragraphs (a) to (m), inclusive.

The results of the life test in relation to the calcium silicon addition to each melt were .as

follows:

Ca Si Fe Zr Percent Percent Percent Percent Calcium silicon 33 62 2.5 Silicon zirconium.' 50 10. 0 36 `In the4 accompanying chart I have graphically illustrated the inuence of boron in combination with a life-imparting diluent upon the factors of workability and increased life in the ilnished product. i More particularly, it .will beseen that the grams calcium silicon content have been set'off as-abscissae, ranging from a minimum of -150 grams to a maximum of 250 grams. The vlife characteristics of alloys containing the previously mentioned proportions of calcium silicon have been set"oi as ordinates.

The curve C represents the result of the tests 4of boron and calcium silicon containing specimens above set-forth. Thus, the point I represents a calcium s i'licon -content of 150\ grams Manganese' Percent boron con- MnB Percent Casi, Casi, Percent Siaddcd ede Tlft Life, tent grains percent boron grams percent Ca from assi pesi v'hours (20% B) CeSi 3 5o- V.085 .017 175 .so .097 .20 .6c .so 155 I have additionallydiscovered that controlled residual quantities of zirconium in conjunction with calcium silicon, when present in an alloy containing nickel, chromium and result in a highly improved life characteristic. For example, employing the same test -method as previously outlined, on nickel-chromium alloys containing the indicated -amounts of boron; zirconium and calcium silicon, life tests of 264 and 149 hours were obtained in products which could be readily worked by conventional methods.v

Thus the life imparting cliaracteristics of boron-` willl which', in conjunction with 5 0 grams of manganese boron. provided a life test of 92 hours.

The point 2 corresponds with the s'econd test specimen in which the calcium silicon content was 160 grains and the life test' -116v hours.'

Point a corresponds with the third test specimen in which 175 grams of calcium silicon provided a life test of 155 hours.

correspondingly, points 4'. and 5 are predicated upon the specimensimilarly numbered in .the

rst table. l

Nowfit will be seen that the curve C is developed by connecting the points1 l, 2; 3, -4' and 5 presence of boron, makes Ifor an unworkable zirconium may be extended through a range whichwould be -unworkable without, the Vaddition of boron.

, In the above enumerated alloys. I foundathat more satisfactory results are obtained by asini;v 'the calcium and zirconium inthe form of alloys or` compounds of ofv their. greater stability in this form." In this connection, it will. be understood lthat direct additions of calcium and zirconium high losses fromoxidation.- Furthermore. calcium vandan' um are readily with the smooth projection.

I have found that a calcium-silicon content in excessot grams, or 0.27% without the product. Thus it may be said that point 2 on the curve C is representative of the limits of Worka-bility, and'consequently the optimumquan-l tity of life-imparting diluent which can be added to the basic alloy without the additional presence of boron.

Examining thev curve furthen'it will be apparent that boron renders the product workable and thus usable and practicable in a commercial sense with calcium silicon content in excess oi' 0.27%. Otherwise stated, the practicable limit of increase in life-imparting diluents has been elevated from 0.27% to 0.42%. This has been shown l by the production of workable materials containing these higher calcium silicon contents and reected in the increase 'in life by the standardtests 1'1'0111 116 to 346 hours.

These commercial forms oi It will be obvious that life tests in excess of 116 hours could not be obtained were it impracticable to manufacture wire to be subjected to the test.

I claim as my invention:

1. A nickel chromium alloy containing 0.34% of a metal of the alkaline earth group, approximately 0.01% of boron, approximately 20% of chromium, the balance nickel.

2. A nickel chromium alloy containing 0.25% to 0.42% of calcium, approximately 0.02% of boron, approximately 20% of chromium and the balance nickel.

3. A nickel chromium alloy containing approximately 0.27% of calcium, approximately 0.02% of boron, approximately 20% of chromium, and the balance nickel.

4. A non-ferrous metal alloy containing nickel approximately 80%, chromium approximately 20%, a metal of the alkaline earth group from substantially 0.27% to 0.42% and boron from 0.02% to 0.01%.

ERICH FETZ. 

